Muffler construction



Sept. 20, 1955 A. .1. DEHAUS MUFFLER CONSTRUCTION Filed Oct. 29, 1951 /ber J De/wous fomey United States Patent Office MUFFLER CONSTRUCTION Albert I. Dehaus, Grand Rapids, Mich.

Application October 29, 1951, Serial No. 253,618

1 Claim. (Cl. 181-42) The present invention relates to noise mutiiers. It is the general function of these devices to progressively withdraw and transform the energy of sound waves passing through a conduit so as to decrease the amplitude of the sound emerging therefrom. These devices are standard equipment on the exhaust lines of internal combustion engines, and in similar installations.

In general, several ways have been devised for removing the energy of the sound wave as it passes through the conduit, and transforming it to heat or into some other form of energy. It is well known to provide a perforated tube in such a conduit, the function of the perforations being to permit the escape of minute quantities of air as each wave front passes along the tube. Progressive withdrawal of such minute quantities of air decreases the amplitude of the pressure gradient at each wave front, and thereby decreases the amplitude of the sound wave that emerges from the conduit. It is also well known that some of the energy of a sound wave may be converted into heat by directing the wave against a movable surface and damping the movement of the surface. The heat energy is dissipated through radiation, convection, or through some sort of cooling system.

The present invention makes use of both of the above principles. A conduit is provided in which a small amount of the gas within the conduit is permitted to escape through the walls thereof as each sound wave moves along. This escaping gas passes into suitable loose ly packed insulating material. The preferred form of the conduit of the present invention is also provided with surfaces arranged generally in a transverse relationship with the axis of the conduit, and these surfaces provide abutments against which portions of the sound wave may be directed. The components forming the conduit walls are movable with respect to each other, and such movement is damped by the presence of the packed material surrounding the conduit. Oscillation of these conduit components under the restraint imposed by the packing serves to convert small amounts of the wave energy into heat, and to thereby reduce the amplitude of the emerging sound waves. The effects described above, when added together by the structure provided by the present inven* tion, serve to produce a very effective mufer with a relatively simple construction.

This construction is capable of being manufactured by standard machines used for other products with but slight modification. The manufacture of armored ilexible cable is similar in many respects to the production of mulilers embodying the present invention, and similar equipment will produce a mutiler section in continuous lengths which may be cut to suit the particular installations. A flexible mufer has the notable advantage of being adapted to installation upon a variety of vehicles. The ability of this unit to be deflected from a straight axis to avoid the frame structure of the automobile, and the possibility of using make shift hanger arrangements rather than specially-manufactured components, makes this device highly desirable for replacement muier units.

The several features of the present invention will be described in detail through an analysis of the particular embodiments illustrated in the accompanying drawings. In these drawings:

Figure 1 is a view in elevation of a muler construction embodying the present invention, with a portion broken away to show an axial section.

Figure 2 is a section taken on the plane 2 2 of Figure 1.

Referring to Figure l, a conduit 10 is shown which is adapted to form a part of an exhaust line of an internal combustion engine. This conduit is formed by the helically-formed strips 10a and 10b, which are substantially S-shaped in cross section, and which are loosely interengaged to form the conduit 10 as shown. It will be noted that the conduit thus formed is flexible, and that a considerable amount of relative movement between the components 10a and 10b is possible. The type of relatively loose engagement between the components is such as to permit a considerable amount of leakage of gas which may be momentarily under pressure within the conduit 10, and thereby permit the escape of gases as each wave front passes such a junction point in its course along the conduit 10. Since the strips 10a and 10b are helically wound, there will be a continuous withdrawal of small quantities of gas under pressure as the wave front moves along, resulting in diminishing the energy of that wave by the time it emerges.

It will also be noted that the configuration of the components 10a and 10b is such as to provide a series of helical surfaces 10c and 10d. These surfaces are substantially transversely arranged with respect to the axis 11 of the conduit, and present abutment surfaces against which portions of the sound waves collide. The action of the sound wave against these surfaces will tend to cause vibration in an axial direction of the components 10a and 10b, and the damping action of the packing material 12 establishes resistance to such movement. These conditions result in the transformation of a considerable amount of the energy of the sound wave into heat. The packing 12 also is useful in damping the sound caused by the emergence of small quantities of gas under pressure around through the juncture of the components 10a and 10b. The presence of a considerable quantity of the loose packing 12 as indicated also serves to control the temperature of the overall unit so that the outer housing 13 does not become overheated. Preferably, the housing 13 is constructed in a fashion similar to the inner conduit 10 so as to preserve the flexibility of the unit.

It is preferred that the packing 12 be asbestos, glass wool, or some other heat-resistant porous material. The housing 13 may take a variety of forms due to the fact that it does not primarily function in the same fashion as does the conduit 10, and acts only to secure the packing in the illustrated form of the invention. In addition to the construction shown, it may also be formed of woven wire or some other similar material. The use of a porous material is only recommended for the simplicity of manufacture. The function of the device does not require porosity in the housing 13; and in fact, the effectiveness of the device would even be increased if no leakage were permitted to go through the housing 13. Due to the minute quantities of gas that would be passing through the packing 12, however, this is not considered to be a necessity. In the event that a sealed housing is used, the volume occupied by the packing 12 forms an adequate reservoir to permit the flow of gas under pressure as the sound waves pass each point of junction between the conduit components. lf a complete seal were effected at the housing, the pressure level within the packing 12 would remain at such a point that backow would take place Paientea sept. 2o, 195s ntothe conduit between the points of high pressure established by the sound waves;

The particular embodiments of the present invention which have been illustrated in the accompanying drawings and are discussed herein are for illustrative purposes only and are not to be considered as alimitation upon the scope of the appended claim. In the claim it is my intention to claim the entire invention disclosed herein except as I am limited by the prior art.

I claim:

A muler for suppressing sound, comprising: conduit means having portions thereof provided with surfacesy by said portions, and bearing against the peripheral surface of said conduit means; and housing means surrounding said conduit means and packing means, and holding said packing means in position against said conduit means.

References Cited in the file of this patent UNITED STATES PATENTS 1,302,300 Brinkman Apr. 29, 1919 1,530,324 Pribil Mar. 17, 1925 2,014,368 Blundell Sept'. 17, 1935 2,096,260 Pavillon Oct. 19, 1937 FOREIGN PATENTS 471,431 Great Britain Sept. 3, 1937 20,266 Denmark June 21, 1915 258.948 Switzerland Dec. 31, 1948 

